摘要:

AbstractMonolayer primary cell cultures of midpregnant mouse mammary cells were subjected to hormone stimulation under strictly defined conditions. Hormonal response was measured in terms of increase in rate of synthesis of mouse casein, using a double antibody precipitation technique. Cells stimulated by insulin plus prolactin plus cortisol plus estradiol plus progesterone showed a marked increase in rate of mouse casein synthesis over the controls. This specific product synthesis, which remains inducible in these cells for at least ten days, was detected either by labelled phosphoric acid or labelled amino acid incorporation. The mouse casein synthesized was identical, as judged by the identification techniques used, to that of mouse milk.Mouse midpregnant mammary explants in organ culture require insulin plus prolactin plus cortisol to express their full lactogenic capabilities. Nevertheless, when the same cells are dispersed and grown in monolayers they require ovarian steroids to elicit a lactogenic response as shown in this study. Ovarian steroids, therefore, are necessary in lactogenesis, although the fundamental nature of their action remains to be established.

ISSN:0022-104X    

DOI:10.1002/jez.1401960102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe blood pressure in the cardinal vein, cardiac chambers and ventral and dorsal aortae have been recorded from conscious eels in water. At low doses, acetylcholine reduced the heart rate but increased the transbranchial differential blood pressure. The effects were abolished by atropine but not by tubocurarine. At doses in excess of 0.1 μg/kg, a secondary rise in arterial blood pressure was observed which could be abolished by bretylium, phentolamine or phenoxybenzamine.Catecholamines did not affect the heart rate although a transient bradycardia due to reflex inhibition could be observed with adrenaline and noradrenaline. Catecholamines increased the cardiac contractile force through an α‐adrenergic mechanism which was blocked by phentolamine but not by propranolol. The relative potency was noradrenaline>adrenaline≫isoprenaline. A β‐adrenergic receptor located in the branchial circulation led to vasodilation and decrease in transbranchial differential pressure. Both α‐(vasoconstriction) and β‐(vasodilation) adrenergic receptors were present in the systemic circulation.Dopamine, 5‐HT, GABA and bradykinin caused bradycardia abolishable by vagotomy or atropine treatment. Angiotensin II was hypertensive but did not affect the heart rate nor the transbranchial differential pressure. Tyramine caused release of endogenous catecholamines. With repeated doses, tachyphylaxis to the drug was observed. Histamine was without any obvious cardiovascular ef

ISSN:0022-104X    

DOI:10.1002/jez.1401960103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractSperm penetration of zonae and fertilization of mouse eggs in vitro was studied as a function of sperm concentration over the range 103−106cells/ml. Maximal fertilization was obtained at 105sperm/ml with markedly reduced levels seen at lower concentrations. Eggs inseminated at low sperm concentrations were, however, characterized by the absence of multiple sperm penetrations of their zonae and by the retention of an intact cumulus oophorus during culture. Penetration levels were similar in eggs inseminated with and without an intact cumulus, although increases in supernumerary and supplemental sperm were observed with partly denuded ova. The distribution of sperm found within eggs inseminated in vitro was compared with a distribution predicted by chance alone. The similarity in observed and expected distributions indicated that a functional zona reaction was absent in eggs inseminated in vitro. Sperm binding to zonae of cumulus‐free unfertilized mouse eggs was shown to be related to sperm concentration over the range 103‐106cells/ml. Zonae sperm binding sites, while too numerous for accurate quantitation, exceeded 100 per zona. The interrelationships between sperm penetration of and sperm binding to the zonae of cumulus‐free eggs were examined. At low sperm concentrations, the ratio of sperm/zonae with bound sperm to sperm/penetrated egg approached one, although the total number of bound sperm exceeded the total number of penetrating sperm. That proportion of cells in a preincubated epididymal sperm suspension capable of binding to the zona was determined and employed in an estimation of the extent of sperm capac

ISSN:0022-104X    

DOI:10.1002/jez.1401960104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractDifferences between ventilatory response and metabolic rates of young rainbow trout tested within the sublethal range of pH 6 to pH 9 were observed using a flowing water respirometer. The oxygen consumption was monitored at swimming speeds of 12 cm/sec and 24 cm/sec. The oxygen consumption rates at 24 cm/sec and pH 6 (423 mg/kg‐hr) and pH 9 (367 mg/kg‐hr) were considerably higher than those determined near neutrality (328 mg/kg‐hr). Ventilation rate increased to either side of neutrality, but significantly fewer respiratory reversals, or “coughs,” were obseved at pH 6 and a greater number at pH 9 than occurred at pH 7 and 8 or in untested fish. The respiratory‐cough response is shown to be pH‐dependent in rainbow trout and may therefore not be as reliable an indication of pollutant‐caused stress in studies where the experimental pH has not been specifie

ISSN:0022-104X    

DOI:10.1002/jez.1401960105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractA differential resorption of the anterior ventral cortical structures is shown to occur in early conjugating pairs ofOxytricha. The member on the pair's left resorbs the collar membranelles and the frontal and right marginal cirri; the member on the pair's right resorbs the central and posterior membranelles (lapel) of the adoral zone of membranelles. The lapel of the left member then aligns with the collar of the right member to form a composite structure which appears with light and scanning electron microscopy to be completely integrated. Consequently, a 4–5‐hour‐old pair contains slightly more than one complete set of anterior ventral organelles (viz., one extra set of undulating membranes) and two complete sets of ventral and anal cirri.Analysis of conjugant pairs in which the two members are joined in abnormal positions suggests that neither the proximity of certain cortical organelles to the region of cytoplasmic bridge formation, the specific pairing position, nor the relocation of certain cortical organelles into a different cortical region is directly responsible for determining which resorption pattern occurs. Furthermore, analysis of the cortical events in conjugating doublets suggests that neither nuclear determination nor differential gene expression can account for the phenomena observed inOxyt

ISSN:0022-104X    

DOI:10.1002/jez.1401960106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe pressures that drive blood in the circulatory systems of marine Crustacea are substantially higher than previously supposed. In recordings from the heart of nine species, absolute pressures (mean of systolic and diastolic) range from 6.7 cm‐H2O to 36.0 cm‐H2O. No relationship is apparent between blood pressure in these species and either wet weight or heart rate. It is proposed that the maintenance of high internal pressures may be of functional significance in Crustacea, both in urine formation by ultrafiltration and in molt

ISSN:0022-104X    

DOI:10.1002/jez.1401960107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractTwo methods of artificial insemination and removal of copulatory plugs were used to investigate the role of the plug in the guinea pig. In addition, the effectiveness of the copulatory plug in blocking the passage of spermatozoa from the second mating was tested in albino females, where coat color was used as a genetic marker.Thirteen female guinea pigs that were either in proestrus, estrus, or metestrus, and inseminated with freshly collected copulatory plugs containing living spermatozoa, did not conceive. In a group of six females from which the copulatory plug was immediately removed, five conceived. Of nine estrous females artificially inseminated, five conceived. In five albino females, copulatory plugs from albino males completely blocked spermatozoa deposited by colored males, and 20 offspring, all albino were born. In a second group of four albino females where the plugs of albino males were removed prior to copulation with colored males, resulting litters were sired by either male or a combination of both males.

ISSN:0022-104X    

DOI:10.1002/jez.1401960108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractIn the absence of the otic capsule, or in the presence of capsular materials of varying volume or placement, the bones and cartilages of the contiguous skull showed several sorts of responses.The parietal and squamosal bones, and possibly the parasphenoid bone and parachordal cartilage apparently used the capsule as a substrate, spreading over its surface.The parietal, squamosal, and exoccipital bones, and the quadrate cartilage were displaced when otic capsule material was absent or oversized.The squamosal bone developed at first independently of the capsule but was modified in its shape and size by the capsule in later, possibly inductive, response.Stresses resulting from paired otic capsules of unequal size bent the parasphenoid bone and the parachordal cartilage through angles of predictable direction relative to the notochord.The paired exoccipital bones developed at different rates when one otic capsule was absent or oversized.The results obtained following manipulation of the otocyst indicate the major role of extrinsic (epigenetic) parameters in normal skeletogenesis and emphasize an apparent discrepancy between the normal and potential expansion of a bone.

ISSN:0022-104X    

DOI:10.1002/jez.1401960109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe results of sperm binding experiments reveal no change in the sperm binding properties of the egg surface coat at fertilization ofUrechis caupoeggs. When fertilized eggs are reinseminated, sperm continue to attach to the egg surface coat. The acrosomal tubules of supernumerary sperm are observed in the perivitelline space closely apposed to the egg membrane. Thus, the polyspermy block inUrechiseggs involves neither alteration of sperm binding sites nor inhibition of the acrosome reaction. Our results suggest that the block is at the level of sperm‐egg membrane fusio

ISSN:0022-104X    

DOI:10.1002/jez.1401960110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe normality of the preimplantation development of 2‐cell to expanded blastocyst stage mouse parthenotes, derived from oocytes activated in vivo, or in vitro, has been assessed at the fine structural level. Major changes in the organization of the cellular organelles, i.e., nucleoli, mitochondria, ribosomes, RER and junctional complexes, follow the same developmental sequences observed in embryos obtained from normally fertilized oocytes. One difference between parthenotes and controls is the scarcity of crystalloid bodies in parthenotes at the blastocyst stage. Because the embryos examined in this study had been cultured in vitro, in a simple salt and albumin medium in the absence of maternal influences, our observations on parthenotes indicate that developmental, preimplantation changes in the subcellular organization of the embryo do not require the continued presence of “maternal” factors or the participation of the paternal g

ISSN:0022-104X    

DOI:10.1002/jez.1401960111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY